The sense of touch is pivotal to survival. When it is corrupted through disease, environmental and homeostatic conditions cannot be sensed, resulting in major physical, experiential and cognitive deficiencies. Furthermore, the sense of touch often becomes the surrogate aid for the deaf or blind, perhaps best exemplified by Braille. In spite of its importance for human survival, comparatively little is known about the sense of touch when compared to hearing and vision. Thus the long-term objective of the research program is to determine the underlying bases for somatosensory sensation and perception. In order to achieve this ultimate goal it will be necessary to determine the relationships among the physical parameters of the stimulus, the underlying physiological and neurochemical mechanisms and the anatomical organization, linking these factors to psychophysical results and behavioral observations. In the short-term, the duration of the proposed research, we will perform anatomical investigations on the hairless (glabrous) skin of mammals (cat, monkey and human), which will test several hypotheses regarding the sense of touch, and lay a basis for future, additional models for taction. For example, we will determine, quantitatively, the organization of Merkel cell-neurite complexes within the skin. Additional experiments will determine nerve-fiber innervation patterns of Merkel cell-neurite complexes and Meissner corpuscles. These results will complement those determined during the previous years of funding. As an outgrowth of the results obtained over the previous years of funding we will also concentrate on the Pacinian corpuscle as a model system. We will determine how the supporting cells (i.e. lamellae) may be involved in transduction mechanisms and whether the mechanosensitive channels found in other mechano-sensitive sensory systems (auditory) are playing a role in transduction within the somatosensory system. This issue is important since recent work from our laboratory indicates the, unlike previous research, the accessory capsule of the PC does not produce flittering of vibratory stimuli but more like creats an environment to assist mechanotransduction. This may also be true of the support cells surrounding the auditory hair cells.